GPFS Error: Unable to delete Client Node from GPFS Cluster

Today when we were delete a Client GPFS Node, the error received was something like:

 Fri Nov  1 11:55:03 SGT 2013: mmaddnode: Processing node node01
mmaddnode: Node node01 was not added to the cluster.
   The node appears to already belong to a GPFS cluster.
mmaddnode: mmaddnode quitting.  None of the specified nodes are valid.

When we do the command mmlcluster, the node was not in the list. So in other words, we are not able to add or delete the node.

Solution: Just reinstall. But you may have to remove old information

# rm -fr /usr/lpp
# rm -fr /var/mmfs

Reinstall and add the GPFS Node again. For more information, do take a look at  Adding nodes to a GPFS cluster